To visit the Thay Pagoda and the Tay Phuong Pagodas you will need an extra day. I did not find tours of these pagodas in any travel agency in Hanoi. If I am not wrong, you will need to book a private tour in order to visit them. It should not be very expensive if you only want someone to bring you here. If you need a travel guide, it will cost you more.
I went here with a Vietnamese friend of mine. We rode his motorbike for more or less one hour. Both pagodas are not far from each other. You can visit both in half a day.